Alternanthera mexicana (Schlecht.) Hieron., Amaranthaceae

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Present on Pacific Islands?  yes

Threat only at high elevations?  no

Habit:  herb

Description:  "Herbaceous.  Stem decumbent, ascending, or erect, often rooting at lower nodes, sometimes scandent, 0.3-1.0 m tall, sparsely to richly branched, glabrous below, more or less pubescent above with subappressed to spreading, shiny and very thin trichomes, leafy internodes 5-20 cm long, stem often thickened at nodes.  Leaves petiolate, petiole 5-15 mm long, pilose; blade mostly thin, lanceolate to ovate or elliptic, cuneate to attenuate at base, acuminate or cuspidate at apex, generally 5-10 cm long and 1.5-5.0 cm wide, glabrous to appressed-pilose.  Flower heads generally long-pedunculate, solitary or 2 or 3 at nodes, sometimes also paniculately arranged in top of plant and at ends of upper branches.  Peduncles filiform, mostly 2-10 cm long, up to ca 1 mm wide, subglabrous to pilose with subappressed to spreading very thin trichomes.  Heads rounded or short-cylindric, 6-10 mm long, 6-7 wide, white or greenish white, 15-50-flowered.  Bract ovate, 1.0-1.5 mm long, acute, wings more or less hyaline, midrib prominent.  Bracteoles longer than bract, rounded-triangular, wings membranous, hyaline, glabrous or sparsely pilose near midrib, midrib prominent, elevated, tending to be free from apical part of membrane, excurrent in a gradually tapering, divergent and often curved point; the excurrent point varying in length from about 0.3 to about 2.5 times the length of the winged part of the bracteole. Flowers sessile or subsessile within bracteoles.  Tepals 5, subequal in length, lanceolate, acute, ca 3 mm long, glabrous to pilose, 3-nerved, often indistinctly so, two innermost (=lateral) tepals boat-shaped, more or less rounded dorsally.  Staminodial tube cleft to about middle, stamens 5, filaments subulate, slightly widened towards base, anthers 0.4-0.7 mm long, pseudostaminodia ligulate, oblong, laciniate at apex.  Ovary rather abruptly narrowed near middle towards base, upper part narrowed into style"  (Eliasson, 1987; pp. 91-93).

Habitat/ecology:  "Found in Ecuador at elevations from about 200 m up to more than 2500 m.  It is an indigenous element of virgin rain forest but also persists in disturbed forests."  (Eliasson, 1987; pp. 91-93)

Propagation:  Seed

Native range:  (native range not known by PIER)

Presence:

Pacific
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Ecuador (Galápagos Islands) Isabela Group	Isabela Island	probably introduced invasive	Charles Darwin Research Station (2005)
Ecuador (Galápagos Islands) Isabela Group	Volcan Sierra Negra	probably introduced invasive	Charles Darwin Research Station (2005)
Ecuador (Galápagos Islands) Santa Cruz Group	Santa Cruz Island	probably introduced invasive	Charles Darwin Research Station (2005)

Pacific Rim
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
Ecuador (Mainland) Ecuador	Ecuador (Republic of) (continental)	native	Eliasson, Uno (1987) (pp. 91-93)

Comments:  Reported as possibly an invasive plant in the Galápagos Islands per Charles Darwin Research Station.

Additional information:  Additional online information about Alternanthera mexicana is available from the Hawaiian Ecosystems at Risk project (HEAR).

Taxonomic information about Alternanthera mexicana may be available from the Germplasm Resources Information Network (GRIN).

References:

Charles Darwin Research Station. 2005. CDRS Herbarium records.

Eliasson, Uno. 1987. Amaranthaceae [44.]. Flora of Ecuador 28. 138 pp.